Groundwater Amendment (draft) Accomack County Comprehensive Plan

[From the U.S. Government Printing Office, www.gpo.gov]

FY 1992 FINAL PRODUCT Task 51
E. Shore Groundwater Ord.

DRAFT GROUNDWATER AMENDMENT

Accomack County Comprehensive Plan

September 30, 1993

FOR DISCUSSION PURPOSES ONLY

Technical Assistance Provided by:
Accomack-Northampton Planning District Commission
P. 0. Box 417
Accomac, VA 23301

A pubtication of the Virginia Deparom t of Environmentat QuaLity's Coastat
Resources Management Program pursuant to mationat Oceanic and Atmospheric
Administration Award No. 027OZO312-01

Draft Comprehensive Plan Ground Water Amendment 9/30/93

GROUND WATER

Introduction
The availability of water will play an increasingly important role
in the development of Accomack County. Accomack County's water
supply is provided by ground water. No major streams or other
surface water supplies exist to supply potable water for human
needs. Because ground water is only replenished by rainfall,
potable drinking water is a renewable but limited resource in
Accomack County.

Background
Ground water is the only source of supply for domestic, industrial,
and agricultural water use on the Eastern Shore of Virginia. A
total population of approximately 45,000 people use this ground
water. Because of the limited supply of ground water, in 1976 the
Virginia State Water Control Board designated the Eastern Shore of
Virginia a "Ground Water Management Area". The Eastern Shore was
the second area in Virginia to be declared a ground water
management area. This declaration was based on the findings that:

- Ground water level declines have been observed in two
sections of Accomack County;

- Interference between wells has been observed in the same
two sections of Accomack County;

- Some evidence of localized ground water contamination has
been observed in the water table aquifer of Accomack
County but not in the confined aquifers;

- Even though the ground water supplies in Accomack County
are not overdrawn and are not expected to be in the near
future, it should be recognized that they may overdraw
in some areas in the future if water withdrawals are not
distributed throughout the region. Further, saltwater
intrusion has not been observed to date but may occur in
the future if heavy ground water withdrawals are
concentrated in any one area.

At the request of Accomack and Northampton Counties, in 1990 the
Accomack-Northampton Planning District Commission commissioned the
development of a Ground Water Management and Supply Protection Plan
to provide a comprehensive and practical series of options,
alternatives and specific actions to promote compatibility between
the Eastern Shore's water resources and the counties' land use
plans.

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Draft Comprehensive Plan Ground Water Amendment 9/30/93

The bi-county Eastern Shore of Virginia Ground Water Study
Committee was formed to oversee the development of the Ground Water
Plan. The Committee consists of two members from each County's
Board of Supervisors, one citizen appointed by each Board of
Supervisors, the County Administrator from each county, and the
Executive Director of the Accomack-Northampton Planning District
Commission. On May 5, 1992 the Committee adopted the Ground Water
Supply Protection and Management Plan for the Eastern Shore of
Virginia. The plan includes a detailed analysis of Eastern Shore
ground water resources and issues, and makes recommendations for
the protection and management of the ground water.

Eastern Shore of Virginia Ground Water Syste
The aquifers on the Eastern Shore are strongly influenced by
geology, rainfall, and ground water use. There are basically two
components to the Eastern Shore ground water system, the upper
Columbia aquifer, and the lower Yorktown-Eastover aquifer.

Columbia Aquifer. The upper Columbia aquifer is unconfined, and is
roughly 80 to 100 feet thick. This aquifer is used primarily for
private on-site domestic wells, and agricultural irrigation.
Approximately 2 million gallons per day are withdrawn from the
Columbia aquifer by private on-site wells for domestic use. Some
portion of the 8.7 million gallons per day withdrawn for irrigation
comes from the Columbia aquifer.

Yorktown-Ea stover Aquifer. The Yorktown-Ea stover Aquifer is a
confined aquifer system consisting of coarse shelly sand found in
three layers that are separated by clay confining units. This
aquifer can range in depth from 80 to 800 below the land surface,
though most wells are pumping form layers between 150 and 300 feet
deep.

Industrial withdrawals and public water supply wells are
exclusively screened in the Yorktown-Ea stover aquifer, while wells
used for agriculture and private household use are withdrawn from
the upper aquifer. Currently 4.5 million gallons per day are
withdrawn from the Yorktown-Eastover aquifer for industrial use and
public water supply.

Ground Water Recharge. Annual precipitation of 42 inches per year
provides the recharge to the Eastern Shore aquifers. Approximately
12-24 inches per year of precipitation recharges the Columbia
aquifer on the Eastern Shore of Virginia. At an average recharge
rate of 17 inches per year, approximately 324 million gallons per
day recharge the Columbia aquifer. Most of this water flows from
the middle of the peninsula and discharges to the Chesapeake Bay
and the Atlantic Ocean, providing an important source of fresh
water for our tidal creeks and bays.

Draft Comprehensive Plan Ground Water Amendment 9/30/93

The clay confining layers that separate the Columbia aquifer from
the Yorktown -Ea stover serve to protect the aquifer from many of the
water quality threats. But the clay confining units also act to
impede the amount and rate of recharge to the aquifer. Only a
small percentage of the precipitation that recharges the Columbia
aquifer contributes to the recharge of the deeper confined aquifer.
It is estimated that only 1.2 inches of precipitation recharge the
Yorktown-Eastover aquifer annually.

Based upon the ground water modelling studies conducted,
approximately 11 million gallons per day is recharged to the
Yorktown-Eastover aquifer. However, it should be noted that this
recharge value is based on average conditions across the entire
Eastern Shore. Depending upon specific site conditions recharge to
the Yorktown-Eastover aquifer may vary by a factor of two.

Ground Water Ouality. Water quality in the Columbia aquifer is
threatened by the many land uses that discharge, leach or dispose
of contaminants to the ground water. Nitrate-nitrogen is the
primary contaminant of concern to the Columbia aquifer. Sources of
nitrate nitrogen include: septic systems; agricultural
fertilizers; manure storage and animal disposal; septage lagoons;
and landfills. In addition, pesticides and underground storage
tanks are also threats.

The average nitrogen concentration in the ground water was
calculated to be 2.0 milligrams per liter. The national drinking
water standard for nitrogen is 10 milligrams per liter. On average
the shallow ground quality is considered very good, however those
areas located down slope from major nitrogen users or disposers may
experience much higher nitrogen concentration.

Ground Water Issues and Concerns
Local planning and elected officials on the Eastern Shore have been
concerned for a number of years about the quality and availability
of ground water. The Virginia State Water Control Board has
conducted several studies and has developed a network of ground
water monitoring wells on the Eastern Shore to document problems.
In addition, through cooperative studies, the U.S. Geological
Survey has developed reports and modelled the hydrogeology. The
results of these investigations all agree that the major ground
water issues are:

- Development Impacts, Septic Systems, Underground Tanks
- Industrial and Public Water Supply Wells
- Well Interference, Salt Water Intrusion
- Agriculture, Water Quality and Quantity
- Animal Wastes
- Adequate Water Supply for Future Demands

Figure 2-5 Generalized EastfWest Cross Section

GENERALIZED EAST / WEST CROSS-SECTION
OF GROUND WATER FLOW ON THE EASTERN
SHORE OF VIRGINIA

WEST lCentral Plateau EAST
Chesapeake PRECIPITATION Atlantic
Bay Ocean

Water Table
Piezometric Level

. ..............

........... ......
....... ...... ........
. . . . . ............. . ....... . . . . ... ....
...... ...... ...............
J:
. . . ... .......

........ ...............
. .. .... .. ...
. ..... .... . .....

v. ........
......... . ....
........ . . .. ...... .. . ... .

. .................

.............

........... ......
.. .... ......

Saft Saft
Gr
ound roun
Water
ater R
f
F
TIT**

Lj Fresh Water Aquifer
E] Fresh Water Aquitard

Ground Water Supply Protection and Maragement Plan for the Eastern Shore of Virginia

Draft Comprehensive Plan Ground Water Amendment 9/30/93

Each of these activities/concerns have an impact on water use and
quality for either the upper aquifer, the lower aquifer or both.
The Ground Water Supply Protection and Management Plan For the
Eastern Shore of Virginia provides a review of each of these
threats.

Adequate Water SupplV for Future Demands

Although it is estimated that there is only 11 million gallons per
day available from the Yorktown-Eastover aquifer, current permits
issued by the Virginia State Water Control Board would allow
withdrawals of up 15.6 million gallon per day from this aquifer.
If this were to occur, problems of well interferences and salt
water intrusion, already observed near the largest industrial water
users, will be greatly enhanced.

Recommendations
Based upon the analyses conducted and the review of existing
information, the study proposes the following actions:

Recommendations for Water Ouality Protection:

- Pursue water conservation measures with major industrial
users.

- Create an overlay protection zoning district to protect
the spine recharge area to the Yorktown-Eastover aquifer;

- Restrict the siting of new mass drainfields in the spine
recharge area;

- Review and revise county zoning and subdivision
regulations; - Require the registration of currently
unregulated underground storage tanks;

- Incorporate ground water protection requirements into
site plan review;

- Develop a private well ordinance to control the siting
and construction of new wells;

- Support the implementation of agricultural nutrient
management plans;

- Implement the provisions of the Chesapeake Bay Program.

FIGURE 2-6.
Conceptual Hydrogeologic Model of Non-Pumping Ground Water Conditions.
on the Eastern Shore of Virginia

Chesapeake Columbia Confining Upper Yorktown -Eastover Upper Yo rktown- Eastover Atlantic
Bay Aquifer Unit Aquifer Confining Unit Ocean

T @@i
. . . . . . . . . . . . .

salt salt
W a ter.,:
Water

. . . . . . . . . . . . . . . .

@4 . ........ .. ..

..........
..... ... ........
. . . ..... .
....... ..
....... ...
............

...........................

Middle Yorktown-Eastover Middle Yorktown-Eastover Lower Yorktown -Eas tove r
Aquifer Confining Unit Aquifer
F-1 Recharge Pathway Flow to Columbia Aquifer
El Recharge Pathway Flow to Upper York town-Eastover Aquifer
I.-

Recharge Pathway Flow to Middle York town-Ea stover Aquifer
Recharge Pathway Flow to Lower Yorktown-Eastover Aquifer

ATLANTIC OCEAN

WPA-A
WPA-B WPA-C
WPA-D WPA-E

6-1;

8 4y
c -S4qcPv

WELLHEAD PROTECTION AREA
(maximum permitted pumping rates)

WELLHEAD PROTECTION AREA
(existing pumping rates)

SPINE RECHARGE AREA
...... ......

li@ 22.000 33.000

Draft Comprehensive Plan Ground Water Amendment 9/30/93

Recommendations for Water Ouantity Management
- Revise State Ground Water Act and Regulations to allow
for re-evaluation of existing permits; ,

- Develop an Eastern Shore Water Management District to
manage water withdrawals;

- Control the siting and development of new water supply
wells to prevent well interference and reduce the threat
of salt water intrusion;

- Continue the Accurate reporting of agricultural water
withdrawals, by well location and depth.

- Continue the consideration of mandatory permitting of
agricultural withdrawals after review of reporting data.

- Protect open space and undeveloped land in the spine
recharge area.

General Recommendations

Implement a land use/water quality data base;

Develop a public education program on ground water.

Continued Research and Investigation

- Investigate the nature of recharge to the Yorktown-
Eastover aquifer;

- Research dilute salt water issues;

- Conduct additional hydrogeologic studies to better define
the geology;

- Evaluate pesticide use on the Eastern Shore;

- Revise the nitrogen Tnodel used in the study over time.

Goals and Objectives for Ground Water Protection
The Eastern Shore of Virginia is situated over a very valuable
ground water resource that is the sole source of water supply to
the inhabitants and is also necessary for both industrial and
agricultural use. Protection of the water quality and quantity
requires the development of goals and objectives designed to
maintain water quality, prevent over use of the aquifer, and

Draft Comprehensive Plan Ground Water Amendment 9/30/93

provide for the future needs to accommodate growth on the Eastern
Shore.

Goals and Obiectives for Ground Water Ouality Protection

Goal: Achieve industrial water conservation.

objective: Work with local industry to develop industrial
water conservation programs.

Goal: Protect the spine recharge area to the Yorktown-
Eastover aquifer.

objective: Restrict the siting of new mass drainfields,
septage lagoons, and landfills, and protect open
space in the spine recharge area.

Goal: Protect groundwater from development impacts such
as overly dense development, failed septic systems,
and leaking underground storage tanks.

objective: Revise county zoning and subdivision regulations to
include development standards and site plan review
which provide for proper land development and
proper siting and construction of septic systems,
private wells, and underground storage tanks.

Goal: Minimize ground water impacts from agricultural
activities.

objective: Provide assistance in developing agricultural
nutrient management plans and implement the
provisions of the Chesapeake Bay Preservation Act.
Goals: Educate the public about proper ground water use
and education.

objective: Develop a public education program on ground water.

Goals and Objectives for Ground Water Ouantity Management

Goal: Re-evaluate existing ground water permits.

objective: Revise State Ground Water Act and Regulations to
allow for re-evaluation of existing permits.

Draft Comprehensive Plan Ground Water Amendment 9/30/93

Goal: Control the siting and development of new water
supply wells to prevent well interference and
reduce the threat of salt water intrusion by
managing Eastern Shore ground water withdrawals.

objective: Develop an Eastern Shore Water Management District
to manage water withdrawals.

Goal: Accurately document agricultural ground water
withdrawals.

objective: Continue the accurate reporting of agricultural
water withdrawals, by well location and depth.

Goal: Accurately document and record ground water
quantity and quality.

Objective: Implement a land use/water quality data base;

Goal: Improve knowledge of Eastern Shore ground water
system.

Objective: Investigate the nature of recharge to the Yorktown-
Eastover aquifer, research dilute salt water
issues, conduct additional hydogeologic studies to
better define the geology, evaluate pesticide use
on the Eastern Shore, revise the nitrogen model
used in the study over time.

Actions for Ground Water Protection and Management
Protection of the water quality and quantity will require the
implementation of many actions designed to maintain water quality,
prevent over use of the aquifer, and provide for the future needs
to accommodate growth on the Eastern Shore.

Actions for Ground Water Ouality Protection

Action: Develop an industrial water conservation program.

Action: Develop regulations to restrict the siting of new mass
drainfields, septage lagoons, and landfills, and to
protect open space in the spine recharge area.

Action: Revise county zoning and subdivision regulations to
include development standards and site plan review which

Draft Comprehensive Plan Ground Water Amendment 9/30/93

provide for proper land development and proper siting and
construction of septic systems, private wells, and
underground storage tanks.

Action: Provide assistance in developing agricultural nutrient
management plans and implement the provisions of the
Chesapeake Bay Preservation Act.

Action: Develop a public education program on ground water.

Actions for Ground Water Ouantity Management

Action: Participate in re-evaluation of existing ground water
withdrawal permits.

Action: Develop an Eastern Shore Water Management District to
manage water withdrawals and control the siting and
development of new water supply wells to prevent well
interference and reduce the threat of salt water
intrusion by managing Eastern Shore ground water
withdrawals.

Action: Document the accurate reporting of agricultural water
withdrawals, by well location and depth.

Action: Develop a land use/water quality data base by accurately
documenting and recording ground water quantity and
quality.

Action: Investigate the nature of recharge to the Yorktown-
Eastover aquifer, research dilute salt water issues,
conduct additional hydogeologic studies to better define
the geology, evaluate pesticide use on the Eastern Shore,
revise the nitrogen model used in the study over time.

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